Finishing compositions are generally applied to textile fibers to improve their subsequent handling and processing. Fiber finishes play an important role in assisting the fiber producer to manufacture the product, and enable the fiber producer's customers to carry out the required yarn and fabric manufacturing processes to obtain the finished textile product. The composition and amount of finish composition applied depend in large measure upon the nature, i.e., the chemical composition of the fiber, the particular stage in the processing of the fiber, and the end use under consideration.
For example, compositions referred to as "spin finishes" are usually applied to textile fibers after extrusion. These or other finishes which may be applied to yarn prior to hitting or winding, and to fiber tows prior to or at the time of crimping, drying, cutting, drawing, roving, and spinning, or to staple fibers prior to carding, i.e., web formation, and subsequent textile operations such as yarn manufacture or preparation of nonwoven webs are commonly called secondary or over-finishes. Such finishes provide lubrication, prevent static build-up, and afford a slight cohesion between adjacent fibers.
The application of such finishes is generally accomplished by contacting a fiber tow or yarn with a solution or an emulsion comprising at least one component having antistatic properties. In addition to a lubricant and anti-static agent, wetting agents, additives such as antioxidants, biocides, anti-corrosion agents, pH control agents, as well as emulsifiers are also commonly found in such finish mixtures. Finish compositions can also be applied to tow, yarn, or cut staple by spraying.
Acceptable finishes must fulfill a number of requirements in addition to providing desired lubricating and antistatic effects. For example, they should be easy to apply (and to remove if desired), they should have good thermal and chemical stability, they should not adversely affect the physical or chemical properties of the fibers to which they are applied and they should aid the subsequent processes to which the treated fibers are subjected, they should not leave residues on surfaces or cause toxic fumes or undesirable odors, they should provide for rapid wetting of fiber surfaces, they should be water-soluble or emulsifiable or solvent-soluble, they should have good storage stability, they should be compatible with sizes, nonwoven binders and other fiber treatments, they should not attract soil or cause color changes to the fibers, they should not interact with frictional elements used in texturizing and they should not be corrosive to machine parts.
Of the numerous compositions which have been proposed as fiber finishes, some of the more noteworthy may be found in the following prior art. For example, U.S. Pat. No. 4,072,617 discloses a finish for acrylic fiber consisting of an alkyl phenol ethoxylated with 40 to 200 moles of ethylene oxide, an amine salt of hydrogenated tallow alcohol phosphate, and a mixture of mineral oil, an ethoxylated aliphatic monohydric alcohol, and the amine-neutralized reaction product of an ethoxylated aliphatic monohydric alcohol phosphate. In addition, U.S. Pat. No. 3,997,450 relates to a finish composition for synthetic fibers such as polyamides and polyesters, consisting essentially of a lubricant selected from a mono- or diester of an aliphatic carboxylic acid with a monohydric aliphatic alcohol, or a refined mineral, animal or vegetable oil; an emulsifier containing up to 50 moles of alkylene oxide per mole of ester, alcohol, or amide wherein the reactive hydroxyl sites of the emulsifiers contain deactivating and cap groups; and an alkali salt of a dialkyl sulfosuccinic acid. Likewise, U.S. Pat. No. 4,725,371 is directed to a finish for the texturing of partially oriented polyester yarn wherein the composition has a pH of at least 10, and comprises an oil-in-water emulsion wherein the oil phase constitutes 2 to 25 weight percent of the emulsion. The oil phase comprises a lubricant selected from mineral oils, alkyl esters, glycerides, silicone oils, waxes, paraffins, naphthenic and polyolefinic lubricants, glycols, glycol esters, and alkoxylated glycol esters. The emulsifiers employed include soaps, glycerol fatty acid esters, sorbitan and polyoxyethylene sorbitan esters, polyglycerol esters, polyoxyethylene esters or ethers, polyoxyethylene polyol ether esters, polyoxyethylene amines and amides, partial polyol ester ethoxylates, sulfated vegetable oils, sulfonated hydrocarbons, and the like.
The purpose of a fiber finish is to provide fiber to metal lubrication and fiber to fiber cohesion, as well as eliminate static electricity. Although much of the basic work to elucidate the mechanisms of lubrication was done in the distant past, results of this work continue to be used to understand and apply results of frictional testing to current problems and the development of new finishes.
The contribution of frictional and antistatic properties can be observed throughout fiber manufacturing and processing. An example is the case of a low denier polypropylene staple fiber which is to be carded into a web and thermally bonded for some disposable nonwoven application. This requires a formulation which in conjunction with the fiber crimp, contributes a relatively high fiber to fiber friction which is important in insuring a carded web with good cohesion, uniformity, and integrity, and which compensates for the low stiffness of the fibers. Low fiber to metal friction is also a key factor in the processing of these staple fibers which have diameters on the order of only 15 to 20 micrometers.
Another example involves a slit film or ribbon type yarn intended for woven carpet backing for tufted carpets. During its manufacture, good wetting of the fiber surface by the finish and moderate frictional coefficients are required. For tufting, however, relatively low fiber to metal friction is a very important feature because of the action of tufting needles on the backing fabric.
Finally, low fiber to fiber friction is a highly desirable feature of continuous filament yarns used in cordage applications which involve twisting and plying to form compact structures which have a large amount of fiber to fiber contact. Low friction is desirable since it is generally associated with high flex resistance, high energy absorption and therefore, long life.
A different area of fiber-to-fiber friction is concerned with continuous filament yarns. This may be illustrated by some examples within the fiber manufacturing plant: package building in spinning and filament drawing or tow drawing are the major steps where the fiber-to-fiber friction is of critical importance. In yarn processing, yarn delivery in coning, stitch formation in knitting, filament damage in braiding, strength and elongation in cordage, slippage of weave in fabric, yarn-to-fabric friction in sewing, are some of the areas where yarn-to-yarn friction is important. Unfortunately, prior art finish compositions fail to provide adequate friction coefficients with respect to the bundle cohesion and scroop of synthetic fiber filaments. This lack of adequate bundle cohesion results in the following problems: migration of filaments from bundles in tri-color yarns resulting in color streaking; difficulty in handling yarns in a direct tuft carpet process in which yarns are not twisted prior to tufting resulting in stray filaments being snagged; the filament twisting process is hindered due to the filaments separating from the main body of the fiber bundle; during fiber manufacture multiple wraps of the multifilament bundles are taken on various rolls wherein the bundles have a tendency to wander resulting in individual filaments from one bundle becoming trapped in an adjacent bundle causing a breakdown in the process.
One commonly used method of increasing both bundle and fiber to fiber cohesion is referred to as air entanglement. This process involves passing air through the fibers so as to promote entanglement, thereby increasing density and cohesion. This process, however, requires the expenditure of capital for the purchase and maintenance of the equipment used for air entanglement, as well as the energy, whether it be gas or electric, required to operate such machinery. All of this added expense clearly is reflected in the production costs of synthetic filament yarns. Hence, it would be highly desirable to provide a composition which, when applied to filament fibers, would accomplish the objectives of enhancing bundle and fiber-to-fiber cohesion, thus eliminating the expense associated with the air entanglement process.
Accordingly, it is an object of this invention to overcome the aforementioned disadvantages of the prior art and provide the afore-noted desired advantages.